American publisher and philanthropist who, with his wife, Lila Bell Acheson (Acheson, Lila Bell), created and published Reader's Digest, one of the most widely circulated magazines in the world.

Wallace was the son of a professor at Presbyterian Macalester College in St. Paul, Minn. He attended Macalester for two years and then left to work in a bank. He began keeping a card index of his favourite articles in current periodicals. He subsequently entered the University of California, Berkeley, and soon met Lila Bell Acheson while staying with a friend in Tacoma, Wash. Wallace successfully condensed some government pamphlets into a booklet on agriculture that he sold, and he was thinking of extending his condensed booklet technique to articles of general interest when the United States entered World War I. Wallace served in the U.S. Army, and, while recuperating from severe wounds, he plotted the magazine digest idea further. He carefully assembled a sample issue in 1920, which he had printed and sent out, one copy at a time, to various publishers, none of whom were interested.

In 1921 Wallace married Acheson, who believed in his idea for a digest. The couple began to publish Reader's Digest by themselves, marketing it by direct mail from a basement underneath a Greenwich Village speakeasy. The first issue appeared in February 1922. The magazine's circulation grew rapidly, rising from 1,500 in 1922 to 200,000 in 1929 and about 23,000,000 (worldwide) in 50 editions and 21 languages by the early 21st century. DeWitt served as editor from 1921 to 1965 and as chairman from 1921 to 1973. The Reader's Digest carried only articles condensed or excerpted from other magazines for 11 years but began to include occasional original articles in 1933 and condensed versions of topical books in 1934. It began to appear in foreign-language editions in 1940, when advertisements were introduced to balance increased distribution costs. As publishers, the Wallaces sought a positive tone—which critics thought banal or reactionary—while printing articles on a wide range of subjects.

The enormous success of the magazine brought them great wealth, and the pair became active in support of numerous philanthropic causes, notably, the restoration of Claude Monet's house and grounds at Giverny, France, and the preservation of temples at Abu Simbel in Egypt. In 1972 the Wallaces were presented with the U.S. Presidential Medal of Freedom. The Lila Wallace–Reader's Digest Fund (reorganized in 2003 as the Wallace Foundation) became a major philanthropic benefactor of the arts and culture.